Yellow-red dye and process of making same.



UNITED STATES PATENT OFFICE.

GADIENT ENGI, OF BASEL, SWITZERLAND, ASSIGNOR TO THE FIRM OF SOCIETY OFCHEMICAL INDUSTRY IN BASLE, OF BASEL,

SWVITZERLAND.

YELLOW- RED DYE AND PROCESS OF MAKING SAME.

Specification of Letters Patent.

Patented Jan. 8,1907.

Application filed May 11,1906. Serial No. 316,309.

To all whom it may concern:

Be it known that I, GADIENT ENGI, chemist, a citizen of the SwissRepublic, and a resi- GH S-G H2.GOOH 1 0 i coon 2 in presence ofaromatic nitro-hydrocarbons such as, for example, nitrobenzeneat hightemperatures. The dyestuff thus obtained dyes cotton without a mordantin an alkaline hydrosulfite vat bluish-red clear tints.

I have now found that dyestuffs of the same character, but dyeingyellower-red tints, may be obtained by heating salicylthioacetic acidwith a nitro-hydrocarbon and an isatin compoundas, for example, isatin,its homologues, and its substitution products. When the mass produced bythe reaction is cooled, the new dyestuffs crystallize in the form ofbrilliant yellowish-red to brownish-red well-formed needles.

The following examples illustrate the manufacture:

Example I: A mixture of ten parts of salicylthioacetic acid and sevenparts of isatin is introduced into about sixty parts of nitrobenzene,and the whole is heated for two to three hours in an oil-bath at 225 to230 centigrade, (temperature of the bath.) On cooling the new dyestuifcrystallizes from the dark yellowish-red solution thus obtained as smallslender yellowish-red crystals, which are separated by filtration,washed with alco hol, and dried. The dyestufl has the followingproperties: In concentrated sulfuric acid it dissolves in the cold to adirty-brown solution. By addition of water to this solution theunchanged dyestufi is precipitated in the form of yellowish-red flocks.By heatingthe dyestuif with concentrated sulfuric acid or feebly-fumingsulfuric acid a beautiful violetish-red solution is obtained whichchanges to a clear brownish red on addition of wa ter withoutprecipitation of the original dyestufi. The diluted sulfuric acidsolution of the dyestulf, which evidently contains a sulfonic acid ofthe dyestuff, dyes wool yellowish-red tints. In the cold the dyestuff isinsoluble in alcohol. It dissolves very difficultly in hot alcohol to aclear rose-colored solution. It dissolves e ually diflicultly in hotbenzene and in hot 0 loroform, yielding bluish-red solutions havingyellowish-red fluorescence. Anilin and nitrobenzene dissolve it easilywhen heated; but it separates com letely on cooling in the form ofbrilliant nee les. With diluted caustic soda andhydrosulfite it forms asolution of a leuco derivative in which cotton may be dyed without aInordant, in the manner of indigo, clear yellowish-red tintscharacterized by their fastness.

Example II: A mixture of twelve parts of salicylthioacetic acid, fiveparts of isatin chlorid, and eighty to one hundred parts of nitrobenzeneis heated in an oil-bath in a vessel provided witha reflux condenser fortwo to three hours, so that it boils gently. When the mass cools, theproduct of the reaction separates as brilliant interlacing brownishredneedles. By filtering these needles and washing them with alcohol theyare obtained directly in a pure condition. thus made behaves withrespect to organic solvents and to concentrated sulfuric acidanalogously to the dyestuff prepared according to Example I.

With caustic soda and hydrosulfite the dyestufl' yields a solution of aleuco derivative capable of dyeing cotton without a mordant in a vat,after the manner of indigo, red tints that are much yellower than thoseobtained with the dyestufi described in my application for LettersPatent, Serial No. 307,413, of March 22, 1906.

The procedure is analogous if the homologues of isatin or its othersubstitution products be used instead of isatin.

What I claim is 1. The described process for the manufacture ofyellowish-red Vat-dyeing dyestufis by heating salicylthioacetic acid s XS.CH2.COO H &

COOH (2) fluorescence, difficultly soluble in hot alcohol with a clearrose coloration, soluble in anilin and nitrobenzene when heated, solublein cold concentrated sulfuric acid with a dirtybrown coloration and inhot concentrated 2o sulfuric acid with a beautiful Violet-red colorationturning to clear brownish red on addition of water.

In witness whereof I have hereunto signed my name, this 1st day of May,1906, in the 25 presence of two subscribing witnesses.

GADIENT ENGI.

Witnesses:

GEO, GIFFORD, OMAND BITTER.

